We share more than food and culture within our homes and communities. We can also spread disease. Luckily, we live in a time when vaccines can protect us from many of the most serious illnesses. Staying current on your shots helps you—and your neighbors—avoid getting and spreading disease.

Vaccines have led to large reductions in illness and death—for both kids and adults—compared with the “pre-vaccine era,” says Dr. David M. Koelle, a vaccine expert at the University of Washington in Seattle. Vaccines will prevent about 322 million illnesses, 21 million hospitalizations, and 732,000 deaths among U.S. children born over the last 20 years, according to a recent report.

Vaccines harness your immune system’s natural ability to detect and destroy disease-causing germs and then “remember” the best way to fight these germs in the future. Vaccination, or immunization, has completely eliminated naturally occurring smallpox worldwide—to the point that we no longer need to get shots against this fast-spreading, once-deadly disease. Polio too has been eliminated in the U.S. and most other nations as well, thanks to immunizations. Poliovirus can affect the brain and spinal cord, leaving people unable to move their arms or legs, or sometimes unable to breathe.

“These childhood diseases used to be dreaded problems that would kill or paralyze children,” says Koelle. “In the 1950s, it was a common occurrence for kids to be fine in the spring, get polio over the summer, and then have to go back to school in the fall no longer able to walk.”

Experts recommend that healthy children and teens get shots against 16 diseases (see Wise Choices box). With this growing list, many disabling or life-threatening illnesses have significantly declined in the U.S., including measles, rubella, and whooping cough. But, unlike smallpox, these disease-causing germs, or pathogens, still exist around the world.

“These days, the risks of not being vaccinated in a developed country, like the United States, may seem superficially safe because of low rates of infection due to vaccination and other advances in public health,” says Koelle. “But we live in an era of international travel where we can be exposed to mobile pathogens.” So even if you don’t travel, a neighbor or classmate could go overseas and bring the disease back to your area.

“When the rates of vaccination drop, there can be a resurgence of the disease,” explains Dr. Saad Omer, a global health researcher at Emory University in Atlanta. For instance, measles was completely eliminated in the U.S. in 2000. But since then, hundreds of travel-related cases have occurred, with a spike of more than 600 measles cases in 2014.

Omer and colleagues examined U.S. reports on measles outbreaks since 2000. “We found that measles cases have occurred mostly in those who are not vaccinated and in communities that have lower rates of vaccination. And that’s true for many vaccine-preventable diseases,” Omer says. Most of the unvaccinated cases were those who chose not to be vaccinated or not to have their children vaccinated for non-medical reasons.

When enough people are vaccinated, the entire community gains protection from the disease. This is called community immunity. It helps to stop the spread of disease and protects the most vulnerable: newborns, the elderly, and people fighting serious illnesses like cancer. During these times, your immune system is often too weak to fend off disease and may not be strong enough for vaccinations. Avoiding exposure becomes key to safeguarding your health.

“There’s a huge benefit to all of us getting the recommended vaccines,” explains Dr. Martha Alexander-Miller, an immune system expert at Wake Forest Baptist Medical Center in Winston-Salem, NC. “Number one, vaccines protect you. But they also limit the presence of disease-causing entities that are circulating in the community. So, you’re helping to protect individuals who may not be capable of protecting themselves, for example because they are too young to get vaccinated.”

When expectant moms are vaccinated, immune protection can pass through the placenta to the fetus. “Early on, the baby’s immune system is immature. So there’s a period of vulnerability where disease and death can occur,” Omer explains. “But the mother’s own antibodies—proteins formed by her immune system—can protect the baby.”

Doctors recommend that moms-to-be get both flu and Tdap (tetanus, diphtheria, and whooping cough) shots, so her body will make antibodies against these diseases. A mother’s antibodies can help protect the newborn until they can receive their own vaccinations.

Some vaccines must be given before pregnancy. Rubella, for instance, can cause life-altering birth defects or miscarriage if contracted during pregnancy. There’s no treatment, but the measles, mumps, and rubella (MMR) vaccine given pre-pregnancy offers prevention. Vaccines for many other common diseases that put newborns at risk are being studied.

“We’ve made amazing progress in the development of effective vaccines,” says Alexander-Miller. “Our ability to have such breakthroughs is the end result of very basic research that went on for years and years. But we still don’t know everything that we need to know about how to create the very best vaccine.” NIH-funded scientists are continuing to search for new ways to stimulate protection against various diseases.

Koelle studies how our bodies fight herpes viruses. There are 8 related herpes viruses, but the body responds differently to each one. So far, we only have a vaccine for one: varicella-zoster virus, which causes chickenpox and shingles.

Koelle’s team is comparing how our immune system responds to chickenpox and the herpes simplex viruses, which cause mouth and genital sores. “We’re hoping to harness the success that has been possible with the chickenpox vaccine and see if we can create a vaccine that would work for both chickenpox and shingles and also herpes simplex,” he says.

Researchers are also working to improve existing vaccines. Some vaccines require a series of shots to trigger a strong immune response. The protection of other vaccines can fade over time, so booster shots may be needed. Some, like the flu vaccine, require a shot each year because the virus changes so that the vaccine no longer protects against new strains. So keeping up with the latest flu vaccines is important.

Ask your doctor’s office whether your vaccinations are current. You may also find records of vaccinations at your state health department or schools. If you can’t find your records, ask your doctor if it’s OK to get a vaccine you might have received before.

Most side effects of vaccines are mild, such as a sore arm, headache, or low-grade fever.

“It can be easy to take vaccines for granted, because you’ll never know all the times you would’ve gotten really sick had you not been vaccinated,” says Alexander-Miller.

Help your community keep diseases at bay: Stay up-to-date with vaccines.

Why immunize our children? Sometimes we are confused by the messages in the media. First we are assured that, thanks to vaccines, some diseases are almost gone from the U.S. But we are also warned to immunize our children, ourselves as adults, and the elderly.

Diseases are becoming rare due to vaccinations.

It’s true, some diseases (like polio and diphtheria) are becoming very rare in the U.S. Of course, they are becoming rare largely because we have been vaccinating against them. But it is still reasonable to ask whether it’s really worthwhile to keep vaccinating.

It’s much like bailing out a boat with a slow leak. When we started bailing, the boat was filled with water. But we have been bailing fast and hard, and now it is almost dry. We could say, “Good. The boat is dry now, so we can throw away the bucket and relax.” But the leak hasn’t stopped. Before long we’d notice a little water seeping in, and soon it might be back up to the same level as when we started.

Keep immunizing until disease is eliminated.

Unless we can “stop the leak” (eliminate the disease), it is important to keep immunizing. Even if there are only a few cases of disease today, if we take away the protection given by vaccination, more and more people will become infected and will spread disease to others. Soon we will undo the progress we have made over the years.

Japan reduced pertussis vaccinations, and an epidemic occurred.

In 1974, Japan had a successful pertussis (whooping cough) vaccination program, with nearly 80% of Japanese children vaccinated. That year only 393 cases of pertussis were reported in the entire country, and there were no deaths from pertussis. But then rumors began to spread that pertussis vaccination was no longer needed and that the vaccine was not safe, and by 1976 only 10% of infants were getting vaccinated. In 1979 Japan suffered a major pertussis epidemic, with more than 13,000 cases of whooping cough and 41 deaths. In 1981 the government began vaccinating with acellular pertussis vaccine, and the number of pertussis cases dropped again.

What if we stopped vaccinating?

So what would happen if we stopped vaccinating here? Diseases that are almost unknown would stage a comeback. Before long we would see epidemics of diseases that are nearly under control today. More children would get sick and more would die.

We vaccinate to protect our future.

We don’t vaccinate just to protect our children. We also vaccinate to protect our grandchildren and their grandchildren. With one disease, smallpox, we “stopped the leak” in the boat by eradicating the disease. Our children don’t have to get smallpox shots anymore because the disease no longer exists. Smallpox is now only a memory, and if we keep vaccinating against other diseases, the same will someday be true for them too. Vaccinations are one of the best ways to put an end to the serious effects of certain diseases.